Yeasts
can be considered man’s oldest industrial microorganism. It’s likely that man
used yeast before the development of a written language. Hieroglyphics suggest
that that ancient Egyptians were using yeast and the process of fermentation to
produce alcoholic beverages and to leaven bread over 5,000 years ago. The biochemical
process of fermentation that is responsible for these actions was not
understood and undoubtedly looked upon by early man as a mysterious and even
magical phenomenon.

It is
believed that these early fermentation systems for alcohol production and bread
making were formed by natural microbial contaminants of flour, other milled
grains and from fruit or other juices containing sugar. Such microbial flora
would have included wild yeasts and lactic acid bacteria that are found
associated with cultivated grains and fruits. Leaven, referred to in the Bible,
was a soft dough-like medium. A small portion of this dough was used to start
or leaven each new bread dough. Over the course of time, the use of these
starter cultures helped to select for improved yeasts by saving a “good” batch
of wine, beer or dough for inoculating the next batch. For hundreds of years,
it was traditional for bakers to obtain the yeast to leaven their bread as
by-products of brewing and wine making. As a result, these early bakers have
also contributed to the selection of these important industrial microorganisms.

It was not until the
invention of the microscope followed by the pioneering scientific work of Louis
Pasteur in the late 1860’s that yeast was identified as a living organism and
the agent responsible for alcoholic fermentation and dough leavening. Shortly
following these discoveries, it became possible to isolate yeast in pure
culture form. With this new found knowledge that yeast was a living organism
and the ability to isolate yeast strains in pure culture form, the stage was
setfor commercial production of baker’s yeast that began around the turn of the
20th century. Since that time, bakers, scientists and yeast manufacturers have
been working to find and produce pure strains of yeast that meet the exacting
and specialized needs of the baking industry.